Writing instrument



FIG. 1 is a front, left perspective view in an exploded condition showing my new design;

FIG. 2 is an elevational view in an exploded condition, all sides of the writing instrument body being identical;

FIG. 3 is a top plan view of FIG. 1; and,

FIG. 4 is a bottom plan view of the writing instrument body shown in FIG. 2. 

The ornamental design for a "writing instrument", as shown and described. 